Internal combustion engines used on agricultural equipment (e.g. mowers) are often exposed to air that contains large quantities of foreign matter. During the normal operation of such engines, a fan draws in air for combustion and/or cooling purposes through an opening in an engine housing, typically called a “blower housing”. Engine grass screens are typically placed over the air intake opening to the engine fan to reduce the amount of foreign matter that passes through the engine fan in to the engine housing. The grass screens are typically designed to rotate along with the engine flywheel or cooling fan so that most of the debris can be shred and shed from the screen, thereby allowing air to flow freely through the engine fan.
Screens that rotate along with an engine flywheel or fan do so very rapidly at high rotational frequencies. Rotating screens are subject to substantial stresses caused by centrifugal forces and engine speed fluctuations during engine operation. In general, it is understood that the first resonant frequency of the screen should typically be more than about two and a half times (2.5×) the rotational frequency of the engine. Accordingly, and as one example, an engine having a running speed of 3600 rpm has a rotational frequency of 60 Hz. Thus, proper screen first resonant frequency of such an engine screen is preferably over 150 Hz (i.e., greater than 2.5 times 60 Hz).
An improved, more durable, engine grass screen assembly that both accommodates a compact engine size and maintains overall engine performance (e.g., power, efficiency, etc.) is desired.